The present invention relates to a tube expander, and more specifically to a tube expander to be used, for example, to expand a plurality of tubes into interlocked relationship with a plurality of radiating fins which together constitute a heat exchanger.
In a tube expander 13 of conventional structure, as shown in FIG. 7, a plurality of tube-expanding mandrels 6 are inserted into a surface 5a of a reciprocating member 5 and fixed therein. Reciprocating member 5 is then moved upwardly and downwardly by cylinders 4 or the like. A stripper plate 7 having strippers 7a to determine the height of projection of the expanded tubes is provided below the reciprocating member 5. Hair pin tubes 9 arranged in a plurality of rows are inserted into a plurality of radiating fins 8 in the same direction. A heat exchanger 11 having end plates 10a, 10b placed on both ends of the radiating fins 8 with the tubes 9 inserted therein is supported by a plurality of receivers 12. Thereafter, the tubes 9 are expanded into a tight interlocked relationship with the end plates 10a, 10b and the plurality of radiating fins 8 by means of pressure applied by mandrels 6 as the reciprocating member 5 descends.
However, a tube expander having the above structure possesses the following problems.
The previously-known tube expander expands a plurality of tubes into interlocked relationship with the end plates and plurality of radiating fins.
However, when the plurality of mandrels are inserted into the plurality of tubes, friction force is generated, which may cause damage to both the tubes and mandrels.
In order to avoid the friction force of the mandrels, it is usually necessary for a worker to manually apply oil to each of the mandrels, which not only leads to extensive time loss in operating the tube expander, but also causes other serious problems such as low productivity.